(1) Field of the Invention
The present invention relates to magenta-anthraquinone dyestuffs for use in sublimation thermaltransfer and to sublimation thermaltransfer sheets comprising one or more thereof.
More specifically, the present invention relates to magenta anthraquinones having good adhesion and color development properties as well as excellent fastness which can be used in a method for producing images using a thermal head for heating and sublimation transfer thereof. The anthraquinones of this application are characterized by high color density and excellent solubility when employed in sublimation thermaltransfer printing sheets, which printing sheets have high transferring speed. In these respects, this invention surpasses the prior art.
The anthraquinones of the present invention are useful for producing colored hard copies through a CRT color display, a color facsimile, a magnetic camera and the like utilizing a transfer type heat-sensitive recording system as the means for recording information.
(2) Description of the Prior Art
Japanese Patent Laid-open Publication No. 78896/1984 discloses the use of compounds represented by the following general formula (A) as a magenta dyestuff for sublimation thermaltransfer: ##STR2##
wherein X is a hydrogen atom or methyl group, and R and R' each is a methyl group, ethyl group or straight-chain or branched propyl or butyl group.
However, dyestuffs having the general formula (A) have poor light fade resistance and thus the preservation of information records employing this dyestuff is defective.
In Japanese Patent Laid-open Publication No. 131293/1985, as magenta dyestuffs for sublimation thermal-transfer there are disclosed anthraquinones which are represented by the following general formula (B): ##STR3## wherein X is an oxygen atom or sulfur atom, and A is a straight-chain or branched alkylene group, alkylene-O-alkylene group, alkylene-S-alkylene group, cyclohexylene group, phenylene group, ##STR4##
However, undesirably a great deal of energy is required to transfer this dyestuff and the cost of a machine which uses this dyestuff is thus uneconomically high.
Moreover, known 1-amino-2-phenoxy-4-hydroxyanthraquinone (CI. No. Disp Red 60), 1-amino-2-phenylthio-4-hydroxyanthraquinone (Japanese Patent Laid-open Publication No. 159091/1985) and 1,4-diamino-2,3 bisphenoxyanthraquinone (Japanese Patent Laid-open Publication No. 268495/1986) are also used, but they have poor in solubility in solvents employed in an ink-based process, they have poor sublimation properties and are unsatisfactory with respect to dyestuff adhesion and fastness properties.
Moreover, these anthraquinone dyestuffs have a yellowish color and therefore magenta dyestuffs in which absorption occurs in a longer wave length range are in strong demand.
Japanese Patent Laid-open Publication No. 227093/1986 discloses an anthraquinone dyestuff, for heat-sensitive transfer recording, represented by the following general formula: ##STR5## wherein R is an alkyl of 2 to 10 carbon atoms, an alkoxy of 2 to 10 carbon atoms, or trifluoromethyl.
Japanese Patent Laid-open Publication No. 138559/1987 discloses an anthraquinone dyestuff represented by the following general formula: ##STR6## wherein R is an alkyl such that the total molecular weight of the anthraquinone is more than 350.
However, recorded images on transfer sheets which comprise a dyestuff having the above general formulas (c) and (d) do not have satisfactory light-fade resistance or color-fastness.